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Abstract

This free-cutting copper alloy includes Cu: more than 58.0% and less than 65.0%, Si: more than 0.30% and less than 1.30%, Pb: more than 0.001% and 0.20% or less, Bi: more than 0.020% and 0.10% or less, and P: more than 0.001% and less than 0.20%, with the remainder being Zn and unavoidable impurities, a total amount of Fe, Mn, Co and Cr is less than 0.45%, a total amount of Sn and Al is less than 0.45%, relationships of 56.5≤[Cu]−4.7×[Si]+0.5×[Pb]+0.5×[Bi]−0.5×[P]≤59.5, and 0.025≤[Pb]+[Bi]<0.25 are satisfied, in constituent phases of a metallographic structure, relationships of 20≤(α)<85, 15<(β)≤80, 0≤(γ)<5, 8.0≤([Bi]+[Pb]−0.002)^1/2×10+([P]−0.001)^1/2×5+((β)−7)^1/2×([Si]−0.1)^1/2×1.2+(γ)^1/2×0.5≤17.0, and 0.9≤([Bi]+[Pb]−0.002)^1/2×((β)−7)^1/2×([Si]−0.1)^1/2≤4.0 are satisfied, and a particle containing Bi is present in α phase.

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